1. Field of the Invention
The present invention relates to a communication controlling apparatus in a local area radio system using a PDC (Personal Digital Cellular) portable terminal unit, in particular, to an audio/non-audio PDC communication controlling apparatus that is connected to a private branch exchange (PBX), that has the same service as a public PDC system, and that provides the service of the PBX.
2. Description of the Related Art
As the number of subscribers to digital portable telephone systems drastically increases, various new services are required. In addition, analog or digital telephone units used in offices and so forth require complicated wiring connections. Thus, fixed telephone units are inconvenient. To solve such problems, radio telephone systems have been constructed.
FIG. 6 is a schematic diagram showing the structure of a conventional radio telephone system as disclosed in Japanese Patent Laid-Open Publication No. Hei6-22360.
In the related art reference shown in FIG. 6, the radio telephone system is composed of a radio terminal unit 617 and a radio terminal unit controlling unit 600. The radio terminal unit controlling unit 600 is connected to a private branch exchange (PBX) or the like (not shown).
The radio terminal unit controlling unit 600 comprises a radio terminal unit communication portion 615, a controlling portion 601, an exchange communication portion 604, a two-wire/four-wire converting portion 610, a hook relay switch 608, a dial relay switch 609, and a selecting switch 611. A modular jack 619 can be used for both a two-wire type interface and a four-wire type interface of the PBX. With two-wire type signal lines 605-R, the radio terminal unit controlling unit 600 is connected to the PBX. A bell detecting portion 607 detects a bell signal received from one of the signal lines 605-R through a capacitor 606. The controlling portion 601 generates a trigger signal. A DTMF (Dual Tone Multi-Frequency) signal generator 612 generates a DTMF signal. The selecting switch 611 selects the trigger signal or the DTMF signal and outputs the selected signal to the PBX or the like.
When an origination call, a termination call, a dialing signal, display data, and so forth are sent and received to/from the PBX, the controlling portion 601 controls the exchange communication portion 604. Such data is transmitted to the radio terminal unit 617 through the radio terminal unit communication portion 615 and an antenna 616.
An audio band signal is sent to the PBX through the radio terminal unit communication portion 615, the two-wire/four-wire converting portion 610, and the modular jack 619.
The controlling portion 601 causes the radio terminal unit communication portion 615 to autonomously search a radio frequency free of an external interference and determine an operation frequency. In addition, the controlling portion 601 causes the radio terminal unit 617 to select a channel through the radio terminal unit communication portion 615.
In other words, according to the related art reference, the controlling portion 601 determines whether or not the interface of the PBX is two-wire type or four-wire type, adaptively converts an audio band signal received from the radio terminal unit 617 into a particular signal, and autonomously determines an operation signal, thereby suppressing the operation frequency from interfering another unit and from being interfered by another unit. However, the radio terminal unit 617 of the system should be disposed in a radio cover area of the radio terminal unit controlling unit 600 accommodated in the PBX.
Thus, in the local area radio system composed of the PBX, the small radio base station, and the radio terminal unit, since communications are available only in the radio cover area of the radio base station accommodated in the PBX, the usability of the system is low.
In addition, since it is difficult to exchange a control signal among a plurality of terminal unit controlling units, while a radio terminal unit is moving, a user thereof cannot communicate to another user.
Moreover, due to the system structure, it is difficult to share the system with a non-audio communication (such as FAX and data communication) and an audio communication.
The present invention is made from the above-described point of view. An object of the present invention is to provide a PDC communication controlling apparatus that has the following features. A PDC portable telephone terminal unit instead of a conventional wired telephone unit used in an office is used in a local area radio system that will be increasingly used year after year. Thus, the PDC portable telephone terminal unit is used as an office telephone unit that has an extension communication function with high mobility. A plurality of PDC portable telephone terminal units can be connected to the PBX. Each PDC portable telephone terminal unit can transmit not only an audio band signal, but a non-audio signal (such as FAX and data). While a PDC portable telephone terminal is moving, it can transmit both an audio signal and a non-audio signal as with a conventional public PDC system. Moreover, services of the PBX are provided. Thus, the usability of a PDC portable telephone terminal unit can be further improved.
A first aspect of the present invention is a PDC communication controlling apparatus, comprising an audio processing means for converting a digital audio signal that has been encoded at a transmission rate of a personal digital cellular (PDC) into a digital audio signal at a transmission rate of a digital exchange network, a small radio base station controlling means accommodating a plurality of small radio base stations that are connected to PDC portable terminal units through radio circuits and that have different radio cover areas, the small radio base station controlling means managing the radio cover areas of the PDC portable terminal units, controlling calls, and controlling and managing the radio circuits, a network-side adaptor used in non-audio communications with the PDC portable terminal units, a PDC/network interface means connected to a private branch exchange through a plurality of communication paths, a time division switch for connecting the PDC/network interface, the audio processing means, the radio base station controlling means, and the network-side adaptor and for switching the connection state thereof under the control of the small radio base station controlling means on time division basis, wherein the small radio base station controlling means separates the PDC/network interface means from the network-side adaptor in the case that a termination call is an audio communication, places the network-side adaptor between the PDC/network interface means and the audio processing means in the case that the termination call is a non-audio communication, and loops back the communication path for an extension communication in the case that the termination call is a communication performed between the PDC portable terminal units.
A second aspect of the present invention is a PDC communication controlling apparatus, comprising an audio processing means for converting a digital audio signal that has been encoded at a transmission rate of a personal digital cellular (PDC) into a digital audio signal at a transmission rate of a digital exchange network, a plurality of small radio base stations having different radio cover areas, a small radio base station controlling means, connected to the small radio base stations, for managing the radio cover areas of PDC portable terminal units, controlling calls, and controlling and managing radio circuits, a network-side adaptor used in non-audio communications with the PDC portable terminal units, a PDC/network interface means connected to a private branch exchange through a plurality of communication paths, a time division switch for connecting the PDC/network interface, the small radio base station controlling means, and the network-side adaptor and for switching the connection state thereof under the control of the small radio base station controlling means on time division basis, wherein the small radio base station controlling means separates the PDC/network interface means from the network-side adaptor in the case that a termination call is an audio communication, places the network-side adaptor between the PDC/network interface means and the small radio base station controlling means in the case that the termination call is a non-audio communication, and loops back the communication path for an extension communication in the case that the termination call is a communication performed between the PDC portable terminal units.
The audio processing means preferably converts an audio signal that has been encoded at a transmission rate of 11.2 kbps, 7.05 kbps, or 3.675 kbps on the PDC side into an ADPCM (Adaptive Differential Pulse Code Modulation) audio signal at a transmission rate of 32 kbps on the digital exchange network side.
Thus, the audio processing means decodes and converts a PDC audio signal at a transmission rate of 11.2 kbps (full rate), 7.05 kbps (half rate), or 3.675 kbps (high efficiency) that has been encoded by a PDC portable terminal unit into an ADPCM signal at a transmission rate of 32 kbps. The resultant signal is sent to the PDC/network interface means by the time division switch. The signal is sent to the PBX through the PDC/network interface means. The PDC/network interface means can directly interface with the PBX. In other words, the PDC portable terminal unit can be connected as an extension unit to the PBX without need to modify the PBX. The PBX detects a destination telephone number from the signal received from the PDC portable terminal, sets a communication path to an external line or an extension line, and calls the telephone unit on the destination side (in the case that the PDC portable terminal unit originates a call).
At this point, the small radio base station (BS) and the radio circuit are controlled by the small radio base station (BS) controlling means. The PDC communication controlling apparatus handles a control signal on the control channel D ch different from the communication channel B ch.
At this point, the small radio base station (BS) controlling means manages the radio cover area of the PDC portable terminal unit and the frequency of the small radio base station. In the PDC communication controlling apparatus, the PDC portable terminal unit can be handed over.
The small radio base station (BS) converts the PDC control signal format into the network control signal format beforehand. The PDC communication controlling apparatus operates corresponding to the network control signal format.
When a non-audio communication (such as FAX/data) is performed, the audio processing means does not perform the encoding/decoding process, but directly send a non-audio signal to the time division switch. The time division switch detects a non-audio signal corresponding to a command received from the small radio base station (BS) controlling means and places the network-side adaptor (modem) in the communication path corresponding to the data type. The network-side adaptor (modem) has a function for terminating the PDC non-audio protocol and converting it into the network-side FAX/data communication protocol or vice versa (T.30, V42. bis etc.).
Thus, the PDC portable terminal unit can be disposed in the radio cover area of the PDC communication controlling apparatus. With the PDC portable terminal unit and the PBX, a local area radio system can be accomplished. In addition, the PDC portable terminal unit can have both services of the public PDC system and the PBX.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings.